Magic T waveguide structures, also known as hybrid Tees, are well known and have been extensively described. See for example pages 306-308 in Principles of Microwave Circuits, Edited by Montgomery, Dicke and Purcell, published by Dover Publications, N.Y. 1965. A magic T commonly involves a four port waveguide structure having effectively four waveguides joined at a junction region with at least one symmetry plane that bisects a pair of input waveguides which are commonly referred to as the E and H input arms or ports. The remaining waveguides are output arms. When the waveguides are coupled to matched loads, power into any one input arm is evenly divided among and coupled to the output arms without transmittal of power to the other input arm.
Since, the power division gives rise to a reflected wave in the input arm, the reflection is elminated by introducing impedance matching elements. These elements typically are symmetrically placed with respect to the symmetry plane in the junction region. The elements may be a post and an iris to respectively provide an impedence match to the input arms.
The waveguides used in the magic T may be conventional rectangular guides or multiple ridge waveguides. The matching elements may be adjustable tuning screws that are typically adjusted for the lowest SWR over the bandwidth of interest. The tuning screws, however, tend to limit the power handling ability of the magic T because of arcing.
Microwave devices have been proposed with a waveguide segment having a reduced cross-sectional area. Such structures have been used in couplers and high power ferrite switches to eliminate the propagation of higher order modes.
Although some of these prior art techniques have been individually applied to achieve moderate power handling ability over a limited bandwidth, a basic shortcoming in available magic T waveguide strucures is that high peak powers (of say in excess of about 20 kilowatts) cannot be accommodated with a low SWR over wide bandwidths that approach a 3:1 bandwidth ratio.